This invention relates to improvements in disc brakes and, particularly, to disc brakes of the type including a stationary member, a pair of friction pads at least one of which being supported slidably on the stationary member, and a caliper slidably supported on the stationary member by at least one pin means and incorporating a hydraulic piston for pressing the back plate of the aforementioned one friction pad.
Usually, the caliper of the disc brakes of the aforementioned type is supported by a pair of parallel pin means and, in applying the brakes, the back plate of one friction pad is pressed directly by the piston against one surface of a rotating disc and the caliper is moved in the opposite direction by the reaction force to urge the other friction pad against the other surface of the disc.
When a brake clearance adjusting device together with a mechanical brake applying device is incorporated in the disc brake of the aforementioned type as shown, for example, in Japanese Patent No. 657380, the rotation of the hydraulic piston must be prevented to attain a satisfactory clearance adjusting function. In such case, the rotation of the hydraulic piston is usually prevented by the engagement of the piston with the associated friction pad, and it is also known to provide a projection and recess engagement between the piston and the friction pad, as shown, in for example, Japanese Utility Model Disclosures No. 51-26290 and No. 51-36773.
In such prior art arrangements, a projection formed on the back plate of the friction pad at a position eccentric to the center of the piston and projecting toward the piston usually engages in a recess formed in the contiguous surface of the piston in the form of a radially extending groove. In releasing the engagement, the friction pad is moved radially outwards with respect to the disc or relative to the caliper. Thus, when the opening in the caliper is not large enough for allowing passage of the friction pad while exchanging the friction pad, it is necessary to disassemble the caliper completely from the disc brake.